Setting alternate syntax file for markdown elements

[paniash]

When opening a *.ipynb file in vim, the converted notebook implements the standard syntax file for markdown which comes with stock vim. I'm trying to use the vim-pandoc-syntax plugin for *.ipynb files and have set this in my .vimrc

augroup pandoc_syntax
    au! FileType ipynb set syntax=markdown.pandoc
augroup END

But this doesn't work at all. Is there any way to change the stock markdown syntax for *.ipynb files when using vimpyter?